This invention relates to new and improved noise attenuating panel and more particularly to a honeycomb panel having a perforated facing sheet with a porous layer bonded thereto allowing communication between the core cells and the atmosphere adjacent to the noise to be attenuated.
In making sound suppressive honeycomb sandwich panels which are exposed to the sound of jet engines and other noise producing mechanisms it is common practice to provide a honeycomb sandwich structure wherein a central backing layer of thin sheet of suitable material is mounted to one face of the core and a facing of thin, perforated, sound pervious sheet material is applied to the other core surface.
Panels of this type construction, although satisfactory for some sound frequencies, are found to be an inefficient noise attenuator over a broad range of frequencies customarily encountered in aircraft jet engines.